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Geostatistics tools like ordinary kriging was utilized to investigate the spatial variation in soil reaction (pH), electrical conductivity (EC), soil organic carbon (OC), calcium carbonate (CaCO3), available nitrogen (N), available phosphorus (P), available potassium (K), DTPA-extractable copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) in hot arid region of Western India. For this, total 132 surface soil samples (0–20 cm depth) were obtained with GPS coordinates from the study area. The study's finding showed that EC showed the highest variability (390%) whereas soil pH showed the least variability (3.72%). The best variogram fit model in ordinary kriging was selected on the basis of largest R2 values. For pH, EC CaCO3, N, K, Zn, and Fe, an exponential model imparted the best variogram fit, while a Gaussian model imparted the best variogram fit for OC, P, and Mn. Semi-variogram analysis (nugget/sill ratio) revealed that EC (0.25), CaCO3 (0.072) and N (0.027) were weakly spatial dependent, whereas pH (0.37), OC (0.456), P (0.598), K (0.70), Mn (0.57) and Fe (0.59) were moderately spatial dependent. However, Cu (1.0) and Zn (0.78) were strongly spatial dependent. The largest goodness-of-prediction criterion (G) values were found for the exponential model for soil pH, EC, CaCO3, N, K, Zn, and Fe while the largest G values were found for the Gaussian model for OC, P, and Mn. The exponential and Gaussian models of ordinary kriging, were able to map the spatial variations in investigated soil-variables. [ABSTRACT FROM AUTHOR]

The study area is situated in the Qelabshowah–Belqas region, known for its Quaternary deposits. This research aims to demonstrate the two-dimensional (2D) variation of subsurface layers and salinity distribution using geoelectrical data, hydrochemical analysis, and geostatistical analysis. DC resistivity measurements were taken at fifteen vertical electrical sounding (VES) survey points using a Schlumberger array (AB/2 = 100 m) along three profiles. In addition, an electrical resistivity tomography (ERT) survey was conducted with a dipole–dipole array across one profile. Seven surface water samples were collected in the area. From the 1D and 2D inversion of VES and ERT data sets, three-to-four geoelectric layers were identified, including unconsolidated surface deposits, saturated clayey sand, saturated sand, and a salt-rich layer. The 2D inversion of VES data revealed an ancient salt-rich layer deposited in swampy conditions over a conductive wet sand layer along profile one due to salt mineral infiltration and dissolution. The 2D inversion of ERT data showed accurate lateral geometric accuracy compared to the 2D inversion of VES data, highlighting geological features, such as caves in the second layer and a buried water canal on the ground surface. Surface water samples showed high salinity levels with sodium hazards, indicating an Na–Cl composition. Geoelectric and hydrochemical data sets were geostatistically analyzed using spherical variogram supported ordinary Kriging interpolation. The analysis indicated weak to moderate spatial dependency for true resistivity parameters, while sodium content (SC) and permeability index (PI) showed strong spatial correlation. The 2D spatial distribution resistivity maps based on the 1D inversion of VES data displayed a general decrease in resistivity with depth, likely due to clay minerals or moist soil in the second layer and saline irrigation water infiltration in the third layer. The 2D spatial distribution of SC and PI showed a high concentration zone, posing a potential risk to agricultural crops regardless of soil permeability. It is recommended to use these maps when cultivating plants that can tolerate high sodium levels during the reclamation process. [ABSTRACT FROM AUTHOR]

This paper compares continuous surfaces obtained by the interpolation of standard penetration test values (Nspt) by depth using deterministic and geostatistical models. The evaluation of the interpolation methods was based on the percent areas of the compactness classes by depth obtained in each method and on the percent errors calculated from the differences between the measured and interpolated Nspt. The Nspt values were obtained from 228 standard penetration tests (SPT) in situ investigations carried out in quaternary sandy marine sediments located along the Brazilian northeast coast. The boreholes are well distributed in an area of 10.9 km, covering six districts of João Pessoa City (Paraíba State, Brazil). The interpolations and analyses were conducted using geographic information system and spreadsheet software. The interpolations of Nspt values were made at depths of 1, 3, 6 and 15 m. The interpolated Nspt values obtained for each depth were classified into five soil compactness classes. The general boundaries of the compactness classes and their percent areas by depth were similar for both methods with some localized differences. Both methods presented high average percent errors and standard deviations, with a slight advantage to the geostatistical model (ordinary kriging). The minimum average percent error and standard deviation occurred at a depth of 3 m for both methods, with a slight advantage to the deterministic method (spline modified). Both methods also indicated a peculiar high soil resistance of the marine sediments at a depth of 6 m and significant areas of loose soils at a depth of 15 m in one of the districts analyzed. Both methods showed similar potential for practical applications for the initial phases of a project, not ruling out more specific SPT tests, but can optimize them. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate variations in groundwater quality parameters between 1990 and 2012, and to assess the suitability of groundwater for irrigation. Groundwater samples were taken in the summers of 1990 and 2012, and hydrochemical characteristics were investigated through Piper and USSL diagrams. The electrical conductivity (EC), sodium percentage (%Na), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), magnesium hazard (MR), potential salinity (PS), and Kelly's ratios (KI) were used as the indicators for the water quality. Water quality parameters were assessed through geostatistical techniques and geographical information systems. Initially, semivariograms were determined for each water quality index, and spatial distribution maps were created for each sampling period through ordinary kriging techniques. Results revealed excessive increases in EC, Na, and Cl values with time. EC values of groundwater were over 1.25 dS/m in 4.64% of the study area in 1990. The area increased to 37.38% in the year 2012. With regard to the Kelly Index, there were not any problems in the study area in 1990, but problems were encountered over 5.75% of the study area in the year 2012. While the ratio of problematic sites with regard to RSC was 2.44% in 1990, the ratio increased to 12.13% in the year 2012. Similar increases were also observed in other water quality parameters except for MR. Higher deteriorations were observed in water quality parameters through the eastern sections of the study area. From 1990 to 2012, increased deteriorations were observed in water quality parameters, and excessive groundwater withdrawal and resultant seawater intrusion were considered as the basic reasons for such deteriorations. Therefore, groundwater withdrawals along the coastal lines should be performed in a controlled fashion, and water quality should continuously be monitored. [ABSTRACT FROM AUTHOR]

Groundwater resources available in the Paleozoic sedimentary formations form the most prolific source of water supply in the Kingdom of Saudi Arabia. In the absence of surface water supplies the available groundwater reserves in these aquifers have been used extensively to fulfill the agricultural and domestic water demands. The main purpose of this paper was to evaluate the groundwater quality in the Northern Western part of Saudi Arabia using the classical water facies diagram (Piper and Durov plot). The more advanced methods of principal component analysis (PCA) for determining the factors controlling the groundwater chemistry and stochastic geostatistics to understand the spatial distribution of different major elements in the groundwater of the study area were employed. 40 groundwater samples from bore wells tapping the Saq aquifer were collected and analyzed for the major ion chemistry and nitrates. Groundwater occurs within detrital sandstones of Phanerozoic era in Saq Formations. Piper plot revealed that most of the water samples belonged to the mixed class (Ca-Mg-Cl-SO type) and few samples falling within the Ca-Mg-HCO type, Na-Cl type, and Ca-Mg-SO type of groundwater facies. Durov plot pointed towards simple dissolution, silicate weathering, ion exchange, and reverse ion exchange as the main processes governing the chemistry of the area. PCA resulted in the extraction of two PC accounting for 78.11 % of the data variability. The extracted PCs pointed towards geogenic factors governing the groundwater quality. Stochastic geostatistics involved prediction maps of ordinary kriging and indicator kriging which provided detailed indications of spatial distribution of the chemical elements. [ABSTRACT FROM AUTHOR]

The Taiwan Island is abundant in spring resources. Many industries of spring spas highlight unique hydrochemical characteristics of springs because consumers frequently consider bathing in all kinds of natural springs with therapeutic and relaxing functions. This work adopted geostatistical approaches, ordinary kriging (OK) and sequential Gaussian simulation (sGs), to spatially explore hydrochemical features of springs in Taiwan and establish classifications of springwater. First, OK and sGs were used to determine chloride, sulfate and bicarbonate distributions of springs emerging from metamorphic and sedimentary rocks. Then, ratios of chloride, sulfate and bicarbonate equivalents per liter were calculated based on the determined distributions. Finally, various combinations of chloride, sulfate and bicarbonate were adopted to spatially characterize classifications of springwater. This research result indicates that OK and sGs are capable of spatially characterizing the hydrochemical features and classification uncertainty of springs. However, the smooth effect of OK underestimates high values and overestimates low values, reducing the difference among Cl, SO and HCO in springwater. Meanwhile, sGs realizations not only present high spatial heterogeneity, but enhance the influence of dominant hydrochemical features on classifications of springwater. Furthermore, springwater emerging from metamorphic and sedimentary rock areas in Taiwan can be divided into eight categories based on combinations of determined chloride, sulfate and bicarbonate. The principal HCO water is the major springwater category. The subordinate springwater types include the principal HCO water with Cl or HCO and the principal Cl water with HCO. [ABSTRACT FROM AUTHOR]

A computer program called jk3d for 3-D ordinary kriging interpolation of scattered data has been developed. A specific feature of the code is that differences of the quality of the measured data are taken into account by weighting them according to the assumed error of the data. The code is demonstrated on subsurface temperature measurements with different measurement errors. One of the main problems when ordinary kriging is used for 3-D subsurface data is a lack of sufficient data for computing the necessary variograms. A feasible procedure to obtain such a variogram is discussed. The final result of the 3-D interpolated temperature data shows, that the quality of the interpolation increases substantially if the measurement error is taken into account. The code uses a modified GSLIB like input. Although not all functions of the GSLIB kriging library are supported, all substantial functions are available. jk3d is LGPL licensed, open source. The current version is available at . [ABSTRACT FROM AUTHOR]

This paper presents the results of electrical resistivity methods in the area delineation that was potentially contaminated by liquefaction products, which are also called putrefactive liquids in Vila Rezende municipal cemetery, Piracicaba, São Paulo, Brazil. The results indicate a depth of water table between 3.1 and 5.1 m, with two groundwater direction flows, one to the SW and another to the SE. Due to the contamination plumes, which have the same groundwater direction flow, as well the conductive anomalies observed in the geoelectric sections, the contamination suspicions in the area were confirmed. The probable plume to the SE extends beyond the limits of the cemetery. The location of the conductive anomalies and the probable contamination plumes showed that the contamination is linked with the depth of the water table and the burial time. Mapping using the geostatistical method of ordinary kriging applied to the work drew structural characteristics of the regional phenomenon and spatial behavior of the electrical resistivity data, resulting in continued surfaces. Thus, this method has proved to be an important tool for mapping contamination plumes in cemeteries. [ABSTRACT FROM AUTHOR]

Analysis of the spatial variability of soil properties is important to explain the site-specific ecosystems. Spatial patterns of some soil properties such as soil texture, exchangeable sodium percentage (ESP), electrical conductivity (ECe), soil pH and cation exchange capacity (CEC) were analyzed in salt and sodic affected soils in the south of the Ardabil province, in the northwest of Iran, to identify their spatial distribution for performance of a site-specific management. Soil samples were collected from 0 to 30, 30 to 60, 60 to 90, 90 to 120 and 120 to 150 cm soil depths at sampling sites. Data were investigated both statistically and geostatistically on the basis of the semivariogram. The spatial distribution model and spatial dependence level varied in the study area. Among the considered parameters, maximum and minimum spatial variability were observed in EC and pH parameters, respectively. Soil properties showed moderate to strong spatial dependence, except for a few. ECe was strongly spatially dependent in the total soil depth and clay was strongly spatially dependent at the first depth. Sand and pH were moderately spatially dependent for three of the five depths. ESP was strongly spatially dependent and silt was moderate in the total soil depths, except at 90-120 cm depth. Furthermore, CEC had strong spatial dependence for three of the five depths. All geostatistical range values were >1,389 m in this study. It was concluded that the strong spatial dependency of soil properties would lead to extrinsic factors such as bedrock, agricultural pollution, drainage and ground water level. [ABSTRACT FROM AUTHOR]

Intensive use of land resources in arid and semi-arid regions exert serious pressures on groundwater resources and jeopardize further socio-economical developments. The Amman-Zarqa Basin (AZB), the most vital basin in Jordan, is facing recent groundwater deterioration due to a very large increase in water demands for domestic, agricultural, and industrial uses. The objectives of this paper were to quantify the degree of contamination in the basin by evaluating the characteristics, distribution and seasonal variations of two pollution indicators (nitrate concentration and salinity) and to determine the impacts of human activities (land use) on groundwater quality. Based upon long-term data (1970–2005) of groundwater samples collected from 538 wells across the AZB, spatial analyses indicated that both indicators have a strong spatial dependence and are anisotropically distributed. Prediction maps of Ordinary Kriging and Indicator Kriging provided detailed indications of the major and minor sources of pollution in the basin. Inefficient wastewater treatment plants, industrial activities and agricultural practices were responsible for 91, 85, and 25% salinization of nearby wells, respectively. Nitrate pollution had reached 73% above threshold (50 mg/L) in some cases. The temporal analyses estimated the salinity buildup rate to be around 8 × 10−2 μS/cm per day, while nitrate buildup rate was estimated to be around 6 × 10−2 mg/L per day. Remote sensing and spatial analyses helped greatly in groundwater quality assessment not only in providing the environmental status of the AZB but also in delineating the potential of contamination risk zones and their correlation to human activities. Furthermore, the paper suggests some environmental protection strategies that should be adopted to protect the vital groundwater resources of the basin from further deterioration. [ABSTRACT FROM AUTHOR]